Method and Device for an Automatic Steering Intervention

ABSTRACT

The invention relates to a method for determining an intensity of an automatic steering intervention of a vehicle. Said intensity is determined in accordance with how solidly a driver holds the steering wheel in his hands or in accordance with how many hands the steering wheel is held.

FIELD OF THE INVENTION

The invention relates to the technical field of those driver assistance systems, which provide an automatic steering intervention for assisting a driver.

BACKGROUND OF THE INVENTION

In the state of the art driver assistance systems are known, e.g. systems to prevent lane departure or emergency steering systems, which provide an automatic steering intervention for assisting a driver.

Furthermore, devices are known in the state of the art, which measure a compressive force applied by the driver to the steering wheel. This can be done capacitively or with optical fibers, which have a lower light transmittance when changing the bend. A steering wheel with an optoelectronic sensor is disclosed in the specification DE196 31 502 C1. The steering wheel is equipped with a fiber optical sensor, which responds to the pressure of the hands of a driver on the steering wheel. The sensor signal varies with the amount of pressure. If e.g. a plurality of pressure sensors is applied to the steering wheel, at least one pressure sensor being arranged in the right region and one pressure sensor being arranged in the left region of the steering wheel, it can be determined whether the driver holds the steering wheel with one or two hands. It is the state of the art to evaluate independently from each other with a plurality of pressure sensors different pressure points on a steering wheel, e.g. rear side left, right or front side, so as to conclude in particular to a driver's intention or driver's attention or a number of hands on the wheel.

Furthermore, it is known in the state of the art to deactivate subject to a driver steering variable a driver assistance system, which influences the steering of a vehicle. In DE 10 2004 057 262 A1 a method and a device for deactivating a driver assistance system influencing the steering of a vehicle subject to a driver steering variable is disclosed, in particular if this driver steering variable exceeds a threshold value. This principle is known for all driver assistance systems as an overruling of the assistance system by a driver.

The driver assistance system claimed in DE 10 2007 052 258 A1 provides that if the driver takes at least one hand on the previously untouched steering wheel, the automatic lateral guidance control of the vehicle changes from the activated in the deactivated state and if the hand is removed from the steering wheel the automatic lateral guidance control is reactivated.

Furthermore, it is the state of the art that a mechanical steering system or an electronically amplified steering system (power steering) or electronic steering system (Steer-by-Wire) in a vehicle converts a steering angle at the steering wheel of a vehicle into a cornering of the vehicle.

Furthermore, driver assistance systems with an automatic steering intervention such as e.g. a driver assistance system for lane keeping (Lane Keeping System) or an emergency steering system or a parking system is known or has already been implemented in today's mass-production vehicles. The driver can recognize the automatic steering intervention by a deflection of the steering wheel.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide an improved method and an improved device for an automatic steering intervention, in particular for the intensity of an automatic steering intervention. The automatic steering intervention in the sense of the invention claimed herein always relates to an activated driver assistance system for an automatic steering intervention such as e.g. a driver assistance system for lane keeping or an emergency steering system or a parking system.

The background of the invention is that the result of an automatic steering intervention—namely, the actual steering angle—is always connected with a driver manual torque simultaneously applied to the steering wheel. If the driver has both hands on the steering wheel the intervention has less influence on the vehicle guidance than would be the case if the driver holds only one hand loosely on the wheel or even is driving freehand. If the driver only loosely holds the steering wheel or holds it not at all, the effect of the automatic steering intervention is stronger than if the driver holds the steering wheel solidly. The driver applies little or no resistance to the automatic steering intervention and thus with the same automatically applied torque the steering wheel is more rotated and a greater steering movement results from the larger steering angle.

It is, therefore, the central idea of the invention to provide a method for determining an intensity of an automatic steering intervention of a vehicle, in which the intensity is determined in accordance with how solidly a driver holds the steering wheel or in accordance with how many hands the steering wheel is held.

Furthermore, it is a central idea of the invention that a threshold value for a maximum allowable intensity is determined in accordance with how solidly a driver holds the steering wheel or in accordance with how many hands the steering wheel is held. In this specification of the invention the idea of security is prevailing. By the given dependence of the threshold value it can be ensured that the vehicle remains controllable for the driver during the autonomous steering operation. This applies in particular for an embodiment of the invention, in which with an increasingly compressive force applied by the driver to the steering wheel or with an increasing number of hands on the steering wheel, the threshold value is increased.

The effectiveness of the automatic steering intervention is thus estimated in advance and is included in the selected intensity or it is ensured that the vehicle remains controllable for the driver even during the autonomous steering movement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a positive embodiment of the invention the intensity is additionally increased, if required by the environmental situation and if the driver holds the steering wheel solidly and/or with two hands, so that even with an increased intensity he could overrule the assistance system with a high probability.

In a preferred embodiment of the invention the intensity is determined in accordance with a driver manual torque or a compressive force applied by the driver to the steering wheel. The compressive force applied to the steering wheel suggests the number of hands on the wheel, in particular if a plurality of pressure sensors is provided at different places on the steering wheel.

Furthermore, on the basis of pressure sensors it can be concluded on the intensity of the connection of the one or two hands with the steering wheel. From this in turn it can be derived how strong an intervention by the driver would be damped or with what reaction the driver could override an intervention.

In a preferred embodiment of the invention the intensity increases with an increasing driver manual torque.

With an increasing compressive force applied by the driver to the steering wheel or with an increasing number of hands on the wheel the intensity is increased, as a stronger damping by the driver can be expected.

In a further embodiment of the invention a maximum allowable intensity is limited by an upper threshold value. This threshold value is chosen in accordance to how solidly a driver holds the steering wheel or with how many hands the steering wheel is held. If the steering wheel is held increasingly solidly in particular with an increasing compressive force applied by the driver to the steering wheel or with an increasing number of hands on the steering wheel, the threshold value is increased.

In a preferred embodiment of the invention the intensity is varied by changing a torque applied to the steering wheel and/or a duration of a torque applied to the steering wheel. The intensity is increased by increasing the torque and/or the duration of the torque.

In particular, the intensity is determined in accordance with a speed of the vehicle. With an increasing speed the intensity decreases, in particular since the intervention, but also the incorrect intervention, stronger affects the driving behavior and the driving situation.

In a further embodiment of the invention the intensity is also determined in accordance with a driver attention detection. The driver attention can be detected e.g. with an interior camera that records the driver's viewing direction. Alternatively, also the driver activity can be assessed, e.g. if the driver actuates the gas or brake pedal or the steering wheel, it can be concluded that the driver is attentive. If the driver is now aware and has two hands on the wheel and/or holds the steering wheel solidly in his hands, a higher intensity can be chosen than if the driver was inattentive.

The invention also provides a device for an automatic steering intervention, which comprises a sensor system for detecting an environmental situation. With the sensor system the necessity of an automatic steering intervention is detected, e.g. if the vehicle departs from the lane or will be doing so shortly. Similarly, an automatic steering intervention can be carried out in case of a risk of collision in order to evade a potential collision object.

Moreover, the device comprises a memory on which a method as described above is stored and a processor for performing a method. Furthermore, a device is provided for outputting a torque to a steering wheel of a vehicle, wherein the strength and/or duration of the torque can be derived from the intensity of intervention. 

1. A method for determining an intensity or a threshold value for a maximum allowable intensity of an automatic steering intervention of a vehicle, wherein the intensity is determined in accordance with how solidly a driver holds the steering wheel or in accordance with how many hands the steering wheel is held.
 2. The method according to claim 1, wherein the intensity is determined in accordance with a compressive force applied by the driver to the steering wheel.
 3. The method according to claim 1, wherein the automatic steering intervention is a component of a steering assistant or an emergency steering assistant or of a system to prevent lane departure.
 4. The method according to claim 1, wherein the intensity is varied by a torque applied to the steering wheel and/or a duration of a torque applied to the steering wheel.
 5. The method according to claim 1, wherein with an increasing compressive force applied by the driver to the steering wheel or with an increasing number of hands on the wheel the intensity is increased.
 6. The method according to claim 1, wherein with an increasing compressive force applied by the driver to the steering wheel or with an increasing number of hands on the steering wheel, the threshold value is increased.
 7. The method according to claim 1, wherein the intensity is determined further in accordance with a speed of the vehicle.
 8. The method according to claim 1, wherein the intensity is determined further in accordance with a driver attention detection.
 9. A device for an automatic steering intervention, the device comprising: a sensor system for detecting an environmental situation, a memory on which a program for performing a method according to claim 1 is stored, a processor for performing the method by executing the program, and a device for outputting a torque to a steering wheel of a vehicle. 